Freezer with liquid cryogen refrigerant and method

A freezer comprising:

• a) an inner vessel defining a storage chamber;
• b) an outer jacket generally surrounding the inner vessel so that an insulation space is defined there between;
• c) a supply of liquid cryogen refrigerant;
• d) a heat exchanger positioned in the storage chamber, said heat exchanger having an outlet and an inlet in communication with the supply of the liquid cryogen refrigerant so that the liquid cryogen refrigerant selectively flows through the heat exchanger to cool the storage chamber while being vaporized;
• e) a purge line in communication with the outlet of the heat exchanger, said purge line including a purge outlet positioned adjacent to an exterior of the heat exchanger;
• and
• f) a purge valve positioned within the purge line so that the vaporized liquid cryogen from the heat exchanger is selectively directed to the exterior of the heat exchanger to reduce ice formation on the heat exchanger.

A method for cooling a storage chamber of a freezer with a liquid cryogen refrigerant comprising the steps of:

• a) providing a heat exchanger in a top portion of the storage chamber;
• b) feeding the liquid cryogen refrigerant to the heat exchanger;
• c) vaporizing the liquid cryogen refrigerant in the heat exchanger using heat from the storage chamber so that the storage chamber is cooled and a cryogen refrigerant vapor is produced;
• d) purging the cryogen refrigerant vapor from the heat exchanger;
• e) directing the purged cryogen refrigerant vapor to an exterior of the heat exchanger to reduce ice formation on the heat exchanger.